1. Field of the Invention
The present invention relates to electrical connectors for flexible boards.
2. Description of the Related Art
Japanese patent application Kokoku No. 4-33671 discloses a low plugging force connector such as shown in FIG. 6. The connector includes a housing 51 having an insertion opening at the upper left corner and a pressure lever 52 attached to the housing for rotation about an axis 52A. The pressure lever 52 is rotatable clockwise up to a pressure position as shown by a broken line, with a convex cylindrical surface 53 thereof sliding on a concave cylindrical surface 54 of the housing 51.
A number of J-shaped contact elements 55 are disposed along the length of the housing 51. Each contact element 55 has a spring contact portion 55A and a connection portion 55B projecting downwardly from the housing 51 through a hole of a printed circuit board P.
The pressure lever 52 has two flat surfaces 52B and 52C joined together to provide an angular pressure edge 52D. When the pressure lever 52 is rotated to the pressure position, the pressure edge 52D moves downwardly along the flexible board F and presses the flexible board F against the contact portions 55A of the contact elements 55.
The use of the electrical connector is as follows. A flexible board F is inserted into a space between the contact elements 55 and the pressure lever 52 which is in an open position as shown in a solid line. Then, the pressure lever 52 is turned clockwise so that the pressure edge 52D moves downwardly along the flexible board F and presses the flexible board F against the contact portions 55A, making connections between the conductors of the flexible board F and the corresponding contact elements 55.
However, when the pressure lever 52 is turned to the pressure position, the contact points or line between the pressure edge 52D and the flexible board F moves downwardly with increasing pressure. That is, the flexible board F receives a downward force.
As a result, the pressure lever 52 receives an upward reactive force. If the reactive force is very large, the pressure lever 52 can come off from concave cylindrical surface 54 of the housing 51.
In addition, the downward force tries to push the flexible board beyond the limit so that the flexible board can be deformed, causing poor connections.